Delivery device having a deflectable and peelable mapping guide sheath for his bundle pacing

ABSTRACT

A delivery device for delivering a pacing lead to the His bundle of a patient&#39;s heart includes an elongated sheath having a distal end, and a plurality of mapping electrodes positioned at the distal end. The distal end of the sheath may have a distal end face, and the mapping electrodes may include two electrodes that diametrically oppose one another at a position exposed on or spaced from the distal end face. The sheath includes a plurality of flexible sections spaced apart from one another, and a pull wire that causes the sheath to deflect from a substantially straight configuration to a dual hinged curved configuration that maneuvers and positions the electrodes in the vicinity of the bundle of His. The sheath may include a PTFE liner having axially oriented, platelet-like fibril features that enable the sheath to be split along its length from a proximal end to the distal end.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of, and claimspriority to, U.S. application Ser. No. 16/452,223, Titled “DELIVERYDEVICE HAVING A DEFLECTABLE AND PEELABLE MAPPING GUIDE SHEATH FOR HISBUNDLE PACING” which was filed on 25 Jun. 2019, the complete subjectmatter of which is expressly incorporated herein by reference in itsentirety.

The present disclosure relates to cardiac resynchronization therapy(CRT), and more particularly to a delivery device comprising adeflectable and peelable mapping guide sheath for locating the bundle ofHis and guiding an electrode lead thereto. Still more particularly, thepresent invention relates to a deflectable and peelable mapping guidesheath that is readily removable from the patient.

BACKGROUND OF THE INVENTION

Cardiac rhythm management systems are useful for electricallystimulating a patient's heart to treat various cardiac arrhythmias. Thecurrent standard of care is to pace the right ventricle by myocardialstimulation. In this technique, pacemaker leads are placed at the apexof the right ventricle and at the AV node, the coronary sinus or theleft ventricle, and a pacemaker sends electrical pulses to these areasof the heart. While effective, this technique can cause abnormalelectrical activation sequences resulting in mechanical ventriculardyssynchrony and an increased risk of heart failure, atrial fibrillationand overall mortality.

An alternative approach has been proposed in which an electrode lead isplaced into the bundle of His located either in the septal wall of theright atrium or subvalvular from the right ventricle also in the atrialseptum. As part of the electrical conduction system of the heart, thebundle of His transmits electrical impulses from the atrioventricular(AV) node to the ventricles of the heart. As the electrical impulsesthat regulate the heartbeat are conducted through the bundle of His fromthe right atrium to the left and right ventricles, a lead placed in orin close proximity to the bundle of His would enable the entireelectrical conduction system to be paced in a physiologically naturalway. Pacing the ventricles in this manner, which closely mimics normalAV conduction, can greatly reduce or eliminate the risks associated withtraditional CRT pacing.

While the improved results obtainable with His pacing have beenrecognized, in practice His pacing is difficult to achieve because thebundle of His is very small and difficult to locate and access with theuse of available or conventional lead delivery devices. The bundle ofHis has a nominal length of about 5 mm and a nominal width of about 2mm. As compared to the ventricles, it generates a relatively faintelectrical signal. As a result of its small size and weak electricalsignal, the bundle of His is extremely difficult to locate by aconventional lead delivery method. Moreover, once the bundle of His hasbeen located, it is difficult using a conventional lead delivery deviceto maintain the position of the lead while it is being affixed to thecardiac tissue. The difficulties involved in locating the bundle of Hisand affixing a pacing lead thereto are reflected in the time it takes toimplant the leads of an electrical stimulation device, such as apacemaker. In a typical case, implanting biventricular leads can becompleted in as little as 1 minute. To the contrary, the placement of asingle lead for His pacing may take 30 minutes or more, frequentlywithout success. In those cases, the physicians typically revert toconventional lead placement at anatomy sites other than the bundle ofHis.

Another difficulty in implanting a His pacing lead concerns removal ofthe delivery device without disturbing the fixation of the pacing leadto the cardiac tissue. In order to prevent the helix of the pacing leadfrom becoming dislodged from the cardiac tissue, it is preferable toapply some forward force or pressure on the lead as the delivery sheathis gradually retracted. This complicates the sheath removal process andbecomes more difficult to do as the partially retracted delivery sheathmakes accessing the pacing lead difficult.

There therefore is a need for improvements to the devices used todeliver and implant electrode leads to make it easier to locate thebundle of His, to accurately implant an electrode therein, and to removethe delivery device once implantation has been completed.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides a delivery device fordelivering a pacing lead to the His bundle of a patient's heart. Thedelivery device includes a handle; an elongated sheath having a proximalend connected to the handle and a distal end remote from the handle, adistal portion of the sheath having a plurality of flexible sectionsspaced from one another along a length of the sheath, the sheath havinga longitudinal rib extending from the proximal end to the distal end andbeing splittable along a first split line from the proximal end to thedistal end; a pull wire having a distal end connected to the sheathdistal to the flexible sections and extending to a proximal end; and aplurality of mapping electrodes positioned on the distal end of thesheath.

Another aspect of the present invention provides a method for deliveringa pacing lead to the His bundle of a patient's heart. The methodincludes providing a delivery device having a sheath with a proximalend, a distal end, a longitudinal rib extending from the proximal end tothe distal end, an axial lumen and a distal end face; inserting thesheath into the patient's body through the superior vena cava until adistal end portion of the sheath is positioned in the right atrium ofthe patient; inserting a pacing lead into the axial lumen of the sheath;deflecting the distal end portion of the sheath so that the distal endface of the sheath confronts the wall of the right atrium; moving thedistal end face of the sheath relative to the wall of the right atriumuntil electrodes on the distal end face of the sheath receive electricalsignals from the His bundle; fixing the pacing lead to tissue at the Hisbundle; and splitting the sheath along a split line from the proximalend to the distal end to remove the sheath from the pacing lead.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present lead delivery device and methods formaking and using the same are disclosed herein with reference to thedrawings, wherein

FIG. 1 is a highly schematic cutaway view of the heart illustrating animplantable cardiac pacing system;

FIG. 2 is a highly schematic cutaway view of the heart showing theposition of the bundle of His relative to other cardiac structures;

FIG. 3 is a diagrammatic view showing the use of a prior art deliverydevice to locate and implant a pacing lead near the bundle of His;

FIG. 4 is a side view of a pacing lead delivery device according to thepresent disclosure;

FIG. 5A is a perspective view showing the layers of the delivery devicesheath and the components used in assembling the sheath;

FIG. 5B is a longitudinal cross-section of the distal portion of thedelivery device sheath;

FIG. 5C is a transverse cross-sectional view of the delivery devicesheath taken along line 5C-5C of FIG. 5B;

FIG. 6 is a perspective view of the inner layer or liner of the deliverydevice sheath shown in FIG. 5A;

FIGS. 7A-7K are transverse cross-sectional views of various embodimentsof the delivery device sheath;

FIG. 8 is an enlarged view of the distal end of the delivery devicesheath;

FIG. 9A is an enlarged side view of the distal tip of the deliverydevice sheath showing the positions of the mapping electrodes thereon;

FIG. 9B is an enlarged view of a portion of FIG. 9A;

FIG. 9C is a highly schematic enlarged longitudinal cross-section of theillustration shown in FIG. 9B;

FIG. 10 is an enlarged view of the distal end of the delivery devicesheath in a deflected condition;

FIG. 11 is a perspective view of one embodiment of a sheath electrode;

FIG. 12 is a perspective view of another embodiment of a sheathelectrode;

FIG. 13 is a perspective view of yet another embodiment of a sheathelectrode;

FIG. 14 is a perspective view of still a further embodiment of a sheathelectrode; FIGS. 15A-D are highly schematic longitudinal cross-sectionsof the sheath electrode of FIG. 13 embedded in a sheath;

FIG. 16 is an exploded view showing a method of assembling the sheathelectrode of FIG. 13 to a sheath;

FIG. 17 is a longitudinal cross-section through the handle of thedelivery device shown in FIG. 4;

FIGS. 18A-B are a schematic end view and a highly schematic longitudinalcross-section, respectively, of a hub connected to a delivery devicesheath;

FIG. 19 is an enlarged view of the distal end of the delivery devicesheath in a deflected condition;

FIG. 20 is a diagrammatic view showing certain distances relative tostructures in the heart;

FIG. 21 is a highly schematic side view of a pacing lead;

FIGS. 22A-D illustrate an in vitro process by which the delivery deviceof FIG. 4 locates the bundle of His and implants a pacing lead therein;

FIG. 23 is a diagrammatic view showing the use of the delivery device ofFIG. 4 to locate and implant a pacing lead in the bundle of His; and

FIGS. 24A-C are highly schematic side views of the proximal end ofvarious embodiments of a pacing lead delivery device, including thehandle, the hub and the electrical connector.

DETAILED DESCRIPTION

As used herein, the terms “proximal” and “distal,” when used inreference to a delivery device, are to be taken as relative to a user ofthe delivery device. “Proximal” is to be understood as relatively closeto the user and “distal” is to be understood as relatively far away fromthe user. As used herein, the terms “substantially,” “generally,” and“about” are intended to mean that slight deviations from absolute areincluded within the scope of the term so modified.

FIG. 1 is a highly schematic cutaway view of heart 10 illustrating theright atrium RA, the right ventricle RV, the left atrium LA, and theleft ventricle LV. During normal operation of heart 10, deoxygenatedblood from the body is returned to the right atrium RA from the superiorvena cava 12 and inferior vena cava 14. The right atrium pumps the bloodthrough the atrioventricular or tricuspid valve 16 to the rightventricle RV, which then pumps the blood through the pulmonary valve 18and the pulmonary artery 20 to the lungs for reoxygenation and removalof carbon dioxide. The newly oxygenated blood from the lungs istransported to the left atrium LA, which pumps the blood through themitral valve 22 to the left ventricle LV. The left ventricle LV pumpsthe blood through the aortic valve 24 and the aorta 26 throughout thebody.

FIG. 2 is another schematic cutaway view showing the location of thebundle of His 30 in the heart. The bundle 30 consists of fast-conductingmuscle fibers that begin at the atrioventricular node in the rightatrium and pass to the interventricular septum. The bundle 30 divides inthe septum into a right branch that travels along the right side of theseptum and supplies excitation to the right ventricle, and a pair ofleft branches that travel along the left side of the septum and supplyexcitation to the left ventricle. The fibers in the branches terminatein an extensive network of Purkinje fibers which distribute excitationpulses to the layer of cells beneath the endocardium.

Returning to FIG. 1, also shown is a schematic view of a prior art Hisbundle mapping and pacing system 50. System 50 includes a subcutaneouslydisposed stimulation device or pacemaker 52 coupled to a pulsing lead 54designed to penetrate the endocardium in contact with His bundle 30.Lead 54 enters the vascular system through one of several possiblevascular access sites and extends through the superior vena cava 12 tothe right atrium RA.

FIG. 3 is a diagrammatic view showing the use of lead 54 to locate thebundle of His 30. While it is being maneuvered through the patient'svasculature to the right atrium RA, lead 54 is held within a protectivesheath 56. In a conventional system, sheath 56 may have a fixed curvethat approximates the position of the bundle of His relative to thesuperior vena cava 12. Once sheath 56 is in the right atrium, the tip oflead 54 is advanced out from the sheath to expose electrodes 60 and 62and helical fixation anchor 64. Electrodes 60 and 62 may be spaced aparton lead 54 by up to about 10 mm. Sheath 56 may be manipulated to advancelead 54 parallel to the atrial wall until the faint electrical signalsfrom His bundle 30 are identified. This typically occurs when electrodes60 and 62 are on opposite sides of the bundle, as depicted in FIG. 3. Atthis point, sheath 56 may be manipulated to implant fixation anchor 64in the atrial wall. However, as fixation anchor 64 is distal toelectrodes 60 and 62, when the electrodes detect the bundle of His 30,the fixation anchor is at a position spaced several millimeters from thebundle. Hence, if implanted at this location, fixation anchor 64 andlead electrodes 60 and 62 will be offset from the bundle of His, suchthat any pacing pulses from pacemaker 52 may not stimulate and pace theHis bundle.

The present disclosure is directed to a special lead delivery deviceconfigured to address the foregoing difficulties in locating andimplanting a lead electrode in the bundle of His 30, and to a sheathconstruction that facilitates removal of the sheath once the leadelectrode has been implanted. One embodiment of a delivery device 100according to the present disclosure is shown in FIG. 4. Delivery device100 includes four major components or assemblies, including a sheath102, a handle 202, a connector assembly 302, and a fluid flushingassembly 241. Connector assembly 302 typically comprises an electricalconnector 340 disposed near handle 202 and provides electricalconnection from the connector 340 to electrodes 310, 312 and to optionalelectrode 350 (FIG. 5B) mounted on the outer surface of sheath 102 nearits distal end, via conductive wires 312 (FIG. 5B) embedded within thesheath. Connector assembly 302 is electrically linked to an externalelectrogram mapping system. Handle 202 contains a hemostasis hub 402 foraccepting and tethering to the proximal portion of sheath 102 andincludes a mechanism for deflecting the distal end of the sheath. Sheath102 has a central opening or lumen through which a pacing lead, via theentrance to hemostasis hub 402, is introduced and advanced distally.Fluid flushing assembly 241 is arranged to connect to hemostasis hub 402leading to the center lumen of sheath 102. Each of sheath 102, handle202, hemostasis hub 402, and connector assembly 302, etc. is describedin more detail below.

Sheath 102 may consist of four sheath sections, including a proximalsection 102 a, a body section 102 b, a deflectable section 102 c and adistal end section 102 d with an atraumatic distal tip 120. Thestructure and configuration of sheath 102 are designed to reliablyintroduce a pacing lead into a patient's heart, while exhibiting a highdegree of maneuverability as provided by the ability to deflect itsdeflectable section 102 c. It is therefore desirable that sheath 102have a sufficient degree of columnar strength for advancement throughthe tortuous vasculature of the patient, and sufficient kink resistanceto bend smoothly. Sheath 102 achieves these characteristics from amulti-layer construction as shown in FIGS. 5A-5C. An inner layer 110 orliner of sheath 102 may be formed from a tube of a lubricious materialto facilitate the passage of a pacing lead through the sheath, as wellas the rotation of the lead within the sheath as it is being fixed toheart tissue. One lubricious material for forming liner 110 may bepolytetrafluoroethylene (PTFE). Liner 110 includes at least one rib orwedge 111 that protrudes radially from the outer surface of the linerfrom the proximal end to the distal end of sheath 102. In a preferredarrangement, liner 110 may include two such ribs 111 that extendsubstantially parallel to one another on diametrically opposed surfacesof the liner. Although ribs 111 are shown as having a square orrectangular cross-section in FIG. 5C, other configurations are possibleas will be described further below in connection with FIGS. 7A-7F.

The liner 110 may be formed from a free-flowing fine powder form of PTFEmixed with a lubricant, such as a hydrocarbon fluid, including, but notlimited to, Naphtha solvents, C₉-C₁₅ hydrocarbons or isoparaffinichydrocarbons, or mineral spirits to create a paste. One or moreparticulate ingredients may be added to the paste, including radiopaquefillers, such as barium sulfate, inorganic pigments, and/or reinforcingnanoclay particles. The paste may be compression-molded into a preformof an appropriate shape, such as a hollow or solid cylinder. The preformmay then be formed into tubular liner 110 using a paste or ram extrusionprocess. Following extrusion, liner 110 may be subjected to a series ofprocessing ovens at sequentially increasing temperatures to flash offthe lubricants and to partially or completely sinter (or thermally fuse)the PTFE powder particles. By ram extruding the PTFE paste at highpressures, the PTFE powder particles will form platelet-like fibrilsoriented in the axial or extrusion direction. Because of weakintermolecular forces between the oriented fibril platelets, liner 110exhibits excellent peelability in its length direction.

PTFE materials exhibit a high degree of chemical inertness andhydrophobicity, and therefore do not readily adhere to other polymers.In order to integrate liner 110 with the other layers of sheath 102, theouter surface of liner 110 may be chemically activated through physicaland/or chemical surface treatment methods, including chemical plasmatreatment or chemical etching processes known in the art. In one suchprocess, a fluorocarbon etchant containing sodium naphthalene may beutilized to chemically treat the outer surface of liner 110 through aseries of process steps, including an etching step, several rinsingsteps and a drying step. In the etching step, liner 110 may be immersedin the etchant at a temperature of between about 55° C. and about 65° C.in a tight vessel with nitrogen purging for a duration of between about30 seconds and a few minutes. Light agitation of the etchant may helppromote the etching effect. Following the etching step, the etchant maybe drained from the vessel and liner 110 may be subjected to a series ofsuccessive rinsing steps, each at a temperature of about 70° C. In thefirst rinsing step, liner 110 is immersed in an alcohol bath(containing, for example, between about 75 wt % and about 90 wt %isopropanol or methanol) for between about 5 seconds and about 20seconds. The alcohol chemically deactivates and partially dissolvessodium naphthalene. In the second rinsing step, liner 110 is immersed inchlorine-free carbon-filtered, distilled or deionized water for betweenabout 15 seconds and about 30 seconds. The second rinsing step may befollowed by a third rinsing step in which liner 110 is immersed in anacidic water bath (containing between about 2 wt % and about 5 wt %acidic acid) for about 60 seconds. The pH of the acidic water bathshould be between about 4 and about 6. The acidity of the bathneutralizes the alkalinity of the etchant and produces a faster and morethorough cleaning effect. Following the rinsing steps, liner 110 may bedried, for example using forced hot air or an oven at between about 70°C. and about 80° C. until fully dried. During the chemical etching ofliner 110, the inner lumen thereof should be sealed off or otherwiseprotected so as to maintain its inherent surface lubricity.

Sheath 102 may comprise a braided layer 112 disposed over liner 110 toenhance its columnar and torsional strengths. Braided layer 112 mayinclude a plurality of metallic braids impregnated with one or morethermoplastic polymers. Examples of acceptable thermoplastic polymersinclude polyamides, such as nylon 11, nylon 12, nylon 612, and the like;polyesters, such as poly(butylene terephthalate), poly(ethyleneterephthalate), and the like; and thermoplastic elastomers, such aspoly(ether-block-amide) copolymer resins, poly(ether-co-ester) blockcopolymer resins, and various thermoplastic polyurethane block copolymerresins. The thermoplastic polyurethane block copolymer resins can havedifferent hard and soft segment chemistries, including, but not limitedto, polyether-based aromatic or aliphatic polyurethanes, polyester-basedaromatic or aliphatic polyurethanes, polycarbonate-based aromatic andaliphatic polyurethanes, silicone-containing polyether-based aromatic oraliphatic polyurethanes, silicone-containing polycarbonate-basedaromatic or aliphatic polyurethanes, or any combinations thereof.Braided layer 112 may include two C-shaped sections 113 a and 113 b,with one section positionable on each side of ribs 111. Sections 113 aand 113 b may extend along the entire length of sheath 102 or may extendonly through the proximal section 102 a and body section 102 b of thesheath.

In one method for forming braided layer 112, a first one of theaforementioned thermoplastic polymers may be extruded onto a mandrelwhose outer diameter is approximately equal to the lumen diameter ofliner 110 to form an inner jacket layer. Multi-thread metallic wires maythen be braided over the inner jacket layer. The wires may be round,with diameters of from about 0.02 mm to about 0.2 mm, or flat, withsizes ranging from about 0.01 mm thick by about 0.05 mm wide to about0.1 mm thick by about 0.20 mm wide. The braid may be woven with aregular, full-load pattern (with one wire passing under two wires andthen over two wires), a diamond pattern (with two side-by-side wiresalternately passing under two side-by-side wires then over twoside-by-side wires), a half-load diamond pattern (with one wire passingunder one wire and then over one wire) or other patterns known in theart.

Following the braiding step, another of the aforementioned thermoplasticpolymers may be extruded over the braids to form an outer jacket layer.The thermoplastic polymers forming the inner and outer jacket layers maybe the same, similar or different. However, they should be chemicallycompatible or miscible so that the polymer of the outer jacket layerstrongly adheres to the polymer of the inner jacket layer as it isextruded thereover. This strong adherence may be achieved by using apolymer with a relatively lower melt temperature for the inner jacketlayer and a polymer with a relatively higher melt temperature for theouter jacket layer. As a result, the polymer of the outer jacket layerwill thermally fuse and strongly adhere to the polymer of the innerjacket layer, embedding the metallic braids therebetween. Once braidedlayer 112 has been formed or pre-made, it may be split in half in thelongitudinal direction using a cutting fixture to form symmetricalC-shaped sections 113 a and 113 b.

Sheath 102 further includes an outer polymer layer 114 disposed over theC-shaped sections 113 a and 113 b of braided layer 112. Outer layer 114extends along the whole length of sheath 102 and preferably providessufficient columnar strength in the proximal section 102 a and bodysection 102 b of sheath 112 and excellent material flexibility in thedeflectable section 102 c as well as material aromaticity in the distalend section 102 d of the sheath. Layer 114 may be formed from differentpolymers capable of being extruded to the desired dimensions and ofproviding varied material stiffnesses or flexibilities as desired,including any of the thermoplastic polymers described above for formingbraided layer 112. Exemplary materials for forming outer layer 114include various chemically similar, but mechanically different, polymermaterials based on a family of poly(ether block amide) copolymer resinssold under the trade name Pebax® by Arkema Inc. Alternatively, polymermaterials used for making outer layer 114 may include other chemicallysimilar, but mechanically different, polymer materials based on a familyof thermoplastic polyurethane resins sold under the trade namePellethane® by Lubrizol Corporation. For the proximal section 102 a andbody section 102 b of sheath 102, outer layer 114 may be formed from atube of a Pebax® or Pellethane® polymer having a hardness of at leastabout Shore D55, preferably from a Pebax® or Pellethane® polymer havinga hardness of about Shore D60 to about D80, and more preferably from aPebax® or Pellethane® polymer having a hardness of about Shore D70 toabout D75. For the deflectable section 102 c of sheath 102, shown moreclearly in FIG. 8, outer layer 114 includes three sections 116, 118, and122. Two sections 116 and 118 of outer layer 114 are made of a lesshard, and therefore more pliable, material than the other section 122.Sections 116 and 118 may also be formed from tubes of Pebax® poly(etherblock amide) or another Pellethane® thermoplastic polyurethaneelastomer, but with a hardness of between about Shore D20 and aboutShore D40, preferably about Shore D35. Sections 116 and 118 each mayhave a length in the axial direction of sheath 102 of between about 1 cmand about 3 cm. In a preferred arrangement, each of sections 116 and 118may have a length in the axial direction of sheath 102 of between about1.5 cm and about 2 cm. Section 116 may be spaced from the distal tip 120of sheath 102 by between about 1 cm and about 3 cm, preferably bybetween about 1.5 cm and about 2.5 cm. Section 118 may be spaced fromsection 116 by between about 0.5 cm and about 2 cm, preferably bybetween about 1 cm and about 2 cm. Section 122 of outer layer 114between sections 116 and 118, and the distal section 124 of outer layer114 (positioned in distal end section 102 d of sheath 102) arepreferably made from the same relatively rigid material as is used toform the outer later in the proximal section 102 a and body section 102b of the sheath. Sections 116 and 118 may be joined to the othersections of layer 114 by gluing, ultrasonic welding, reflow heating orother known techniques. In a preferred arrangement, the distal tip 120of sheath 102 may be formed from Pebax® or another polymer that issofter than the material forming the distal section 124 of outer layer114 so as to provide an atraumatic tip to the sheath. In someembodiments, the polymers forming outer layer 114 may include radiopaquefillers, such as barium sulfate, tungsten, bismuth trioxide, bismuthsubcarbonate, bismuth oxychloride and the like. Polymers containing aradiopaque filler may be used for outer layer 114 in different sectionsof sheath 102.

Despite the fact that different sections of outer layer 114 may beformed from different materials, the polymers forming the differentsections may first be extruded as continuous tubes and then cut tolengths. Depending on the cross-sectional configuration of sheath 102,as shown in FIGS. 5C and 7A-K, the sections of outer layer 114 may beslit in the longitudinal direction to form symmetrical C-shapedsections. Where outer layer 114 is to be assembled to sheath 102 in atubular form without slitting, as in FIG. 5C, the outer layer ispreferably extruded with one or more inner recesses 115 that correspondin shape and size to the ribs 111 on liner 110.

A lumen 126 (FIG. 5B) extends continuously through sheath 102 along itsentire length. Lumen 126 has a diameter that is slightly larger than thediameter of the pacing lead to be delivered to the heart by deliverydevice 100. For example, for a 7 French pacing lead (having a diameterof about 2.33 mm), lumen 126 may have a size of about 7.5 French (adiameter of about 2.5 mm).

A pull wire 130 may extend through a narrow tube 132 extending along thelength of sheath 102 between braided layer 112 and outer layer 114. Inan alternate arrangement, tube 132 may be positioned between liner 110and braided layer 112. Tube 132 is preferably formed from a materialthat will resist collapsing or kinking during the manufacture of sheath102 and the use of delivery device 100. Materials appropriate forforming tube 132 include polyetherimide, polyimide, PTFE or other hightemperature polymers. Optionally, tube 132 may include metal braids tofurther enhance its kink resistance. Pull wire 130 may be welded orotherwise affixed at its distal end to a pull wire ring 134 and may beconnected at its proximal end to an operating mechanism in handle 202,described more fully below. Pull wire ring 134 is axially located in thedistal end section 102 d of sheath 102 and is fixed in place betweenbraided layer 112 and outer layer 114 or between liner 110 and braidedlayer 112. Although referred to as a “ring,” pull wire ring 134 mayactually consist of one C-shaped section that may be positioned on oneside of ribs 111, or two C-shaped sections that are not connected to oneanother, but that may be positioned on opposite sides of ribs 111. Assheath 102 need only be deflected in a single direction, a singleC-shaped section may be positioned on the side of the sheath towardwhich deflectable section 102 c is to be deflected. Tube 132 for pullwire 130 would be positioned on the same side of sheath 102 as theC-shaped portion of pull wire ring 134.

The distal end section 102 d of sheath 102 also includes a pair of splitmapping electrodes 310 and 312, as shown in FIGS. 5B and 9A. Electrodes310 and 312 are electrically connected to connector assembly 302 viaelectrical conductor 314, and they may be identical to one another. Anyappropriate metal, such as platinum-iridium, may be used to formelectrodes 310 and 312, and they may be diametrically opposed to oneanother on opposite sides of sheath 102. For a sheath having aconventional size, the ends of electrode 310 may be spaced apart in thecircumferential direction from the ends of electrode 312 by betweenabout 1 mm and about 3 mm, preferably by about 2.5 mm. An electricalconductor 314 may extend from each of electrodes 310 and 312 through anarrow tube 140 extending along the length of sheath 102 between braidedlayer 112 and outer layer 114 or between liner 110 and braided layer112. Tube 140 may be formed from the same polymer used to form tube 132and may optionally include metal braids to enhance its kink resistance.Upon exiting tube 140, conductors 314 may travel through a lumen (notshown) in handle 202 and through a conduit 320 to an electricalconnector 340 (FIG. 4). As will be explained further below, electrodes310 and 312 are preferably positioned at the distal tip 120 of sheath102, or very close to the distal tip, and on opposite sides of ribs 111.

The fabrication of sheath 102 will now be described with reference toFIGS. 5A to 5C. To fabricate sheath 102, its individual components maybe sequentially assembled over a supporting core rod 500. Thus, aftertreatment of its outer surface, liner 110 may be assembled over core rod500, followed by sections 113 a and 113 b of braided layer 112 on eitherside of ribs 111. Pull wire ring 134 (i.e., at least one C-shapedsection thereof) may then be positioned over braided layer 112 in thedistal end section 102 d of sheath 102, and tube 132 containing pullwire 130 that has been pre-welded to the pull wire ring may bepositioned alongside the braided layer. Alternatively, tube 132 may bepositioned against liner 110 and sections 113 a and 113 b of braidedlayer 112 may be assembled thereover. Pull wire 130 extends from pullwire ring 134 through tube 132 and out from the proximal end thereof.Similarly, tube 140 is properly positioned, and electrical conductors314 may be threaded through tube 140 and out from the proximal endthereof. As will be appreciated from the discussion below, a C-shapedsection of pull wire ring 134, tube 132 and pull wire 130 preferably arepositioned along the side of braided layer 112 toward which sheath 102is to be deflected. Tube 140 and electrical conductors 314 may bepositioned on the side of braided layer 112 diametrically opposed totube 132 or at another position around the circumference of the braidedlayer. However, neither tube 132 nor tube 140 should be positioned inclose proximity to a rib 111 as such positioning could interfere withthe peelability of sheath 102. The sections of outer layer 114corresponding to the different sections of sheath 102, includingproximal section 102 a, body section 102 b, deflectable section 102 c(namely sections 116, 118, and 122 of outer layer 114), and distal endsection 102 d (namely section 124 of outer layer 114) with distal tip120, may then be assembled over the previously assembled components.Depending on the cross-sectional configuration of sheath 102, thesections of outer layer 114 may be assembled to the other componentseither as sections of full tubes or as C-shaped tube sections. When allof the individual components of sheath 102 have been assembled togetherand their relative positions have been properly adjusted, aheat-shrinkable tube 510 may be applied thereover to fully encapsulatethe assembly. When heated in a reflow process to an appropriate thermallamination temperature near or above the critical thermal transitiontemperatures of the polymers used for braided layer 112 and outerpolymer layer 114, the polymers in those layers will partially orcompletely melt, thermally bonding the layers to one another and toliner 110. Liner 110, on the other hand, will not melt, so that itsaxially oriented platelet-like fibrils will remain intact. However, thechemical etching of the outer surface of liner 110 will cause thepolymers of braided layer 112 to strongly adhere to it.

Although braided layer 112 was described above as including metal braidsimbedded in inner and outer polymer jacket layers, that may not be thecase. In an alternate embodiment, braided layer 112 may be formed simplyby forming the metal braids on a disposable mandrel without the polymerjacket layers. The metal braids may be formed into a tubular shape andassembled to the other sheath components in the tubular form or may becut longitudinally to form two C-shaped sections. In either arrangement,the individual components of sheath 102 would be assembled as describedabove. That is, the metal braided layer 112 would be assembled overliner 110 (and over or under tubes 132 and 140), pull wire 130, pullwire ring 134, electrodes 310 and 312, conductors 314, and relevantconstraining tubes 132 and 140 would be properly positioned, and thenthe sections of outer layer 114 would be assembled thereover. During thesubsequent reflow process, the polymers of outer layer 114 will melt,permeate the metal braids and thermally fuse to bond with liner 110.

As electrodes 310 and 312 are split mapping electrodes that do not fullycircumscribe sheath 102, the electrodes must be strongly attached to thesheath so as to not become detached therefrom upon advancement of thesheath through the patient's vasculature to deliver a pacing lead to thebundle of His 30 or during removal of the sheath from the patientfollowing such procedure. Thus, while electrodes 310 and 312 may bepositioned at the tip of sheath 102 to thereby be exposed on the distalend face of the sheath, the electrodes are preferably spaced from thetip of the sheath so as to be surrounded on all sides by a continuousmass of the sheath polymer.

FIGS. 9A-C illustrate the positions of electrodes 310 and 312 at thedistal tip 120 of sheath 102. The positions of electrodes 310 and 312 onsheath 102 are based generally on two considerations—obtaining thestrongest signal from the bundle of His and assuring the adherence ofthe electrodes to the sheath. As noted, it is preferable to spaceelectrodes 310 and 312 from the tip of sheath 102 to more securelyadhere the electrodes to the sheath. However, the ability of theelectrodes to sense signals from the bundle of His is greatest when theelectrodes are exposed on the distal end face of the sheath. As acompromise, it is preferable to position the electrodes as close aspossible to the distal end face of sheath 102 while still allowing aregion 150 of polymer between the electrodes and the tip of the sheath.In one embodiment, recessing the electrodes about 0.5 mm from the tip ofsheath 102 is preferred. In addition to more securely fixing theelectrodes to sheath 102, spacing the electrodes proximally of thedistal tip of the sheath keeps sharp edges of the electrodes from beingexposed, thereby reducing trauma to tissue as delivery device 100 isadvanced through the patient's vasculature. As shown in FIG. 9B, the tipof sheath 102 also may be chamfered, as at 152, further reducing traumaduring the advancement of delivery device 100. Making the distal end ofsheath 102 black or another dark color, as shown in FIG. 10, willhighlight metallic electrodes 310 and 312 and make them more visible.

Another consideration in where to position electrodes 310 and 312 onsheath 102 has to do with the direction in which the distal tip of thesheath deflects. In that regard, it is preferable to position theelectrodes on sheath 102 so that, when the sheath is deflected, theelectrodes are generally aligned in the direction in which the fibers ofthe bundle of His are oriented. The maximum signal will be detected fromthe bundle of His when both electrode 310 and electrode 312 are locateddirectly thereover. Thus, if electrodes 310 and 312 are oriented onsheath 102 on opposite sides of the deflection plane defined by thedeflected distal tip of the sheath (i.e., at positions located 90° fromthe positions shown in FIG. 10), only one electrode at a time will beable to be located over the bundle of His 30. As sheath 102 is movedrelative to the atrial septal wall in an area in close proximity to theHis bundle, one electrode may move closer to the His bundle while theother electrode may move away from the His bundle, such that the maximumpossible signal will not be obtained. On the other hand, by positioningboth of electrodes 310 and 312 in the deflection plane, shown in dashedlines in FIG. 10, both electrodes can lie over the bundle of His 30 atthe same time. In fact, as sheath 102 is moved across the atrial septalwall, there will be a distance equal to about the diameter of the sheathwithin which the maximum His bundle signal can be detected.

In order to assemble electrodes 310 and 312 to sheath 102, a portion ofthe polymer is first removed from areas on opposite sides of the distalend of the sheath, creating cavities 154 and 156 sized to receive theelectrodes. Cavities 154 and 156 may be formed either before or afterassembling the components of sheath 102. In one example, the polymer maybe removed by laser ablation, although other removal techniques known inthe art may also be employed, including but not limited to cutting,grinding, chemical etching and the like. Preferably, the polymer isremoved to a depth that is substantially the same as the radialthickness of electrodes 310 and 312 so that, once assembled to sheath102, the outer surface of the electrodes will be substantially flushwith the outer surface of the sheath. After a conductor 314 has beenassembled to each of electrodes 310 and 312, the electrodes are insertedinto cavities 154 and 156, respectively, and the distal end of thesheath may again be subjected to a reflow heating process to partiallyor completely melt the outer polymer of braided layer 112 and outerpolymer layer 114 to mechanically interlock the electrodes with thesheath's polymer material. FIG. 9C is a cross-sectional view showingelectrode 310 embedded within the polymer at the distal end of sheath102.

FIGS. 11-16 illustrate examples of structures for forming electrodes 310and 312 to facilitate their secure assembly to sheath 102. Each of thecurved structures shown in these figures may be laser cut or otherwiseformed from a metal tube having a circumference that is substantiallysimilar to the circumference of sheath 102 so that the curvature of theresultant electrodes matches that of the sheath. Structures not shownwith a curved configuration may be formed flat from flat sheet stock andsubsequently bent to have a curvature that matches the curvature ofsheath 102.

The electrode 800 shown in FIG. 11 is generally in the form of a plate802 having a curvature that is substantially similar to the curvature ofthe outer surface of sheath 102. The side edges 804 a and 804 b of plate802 (i.e., the edges that are substantially parallel to the longitudinalaxis of sheath 102) are beveled so that, during the reflow heatingprocess, the softened or molten polymer can flow over the beveled edgesto securely hold electrode 800 to the sheath. Rather than the side edgesof plate 802 being beveled, electrode 800 may be formed so that the endedges 806 a and 806 b of plate 802 (i.e., the edges that aresubstantially orthogonal to the longitudinal axis of sheath 102) may bebeveled, or both the side edges and end edges may be beveled. Plate 802may optionally include an aperture 808 that may fill with polymer duringthe reflow heating process to further prevent electrode 800 from movinglongitudinally relative to the sheath.

In the embodiment shown in FIG. 12, a generally flat metal plate 902 maybe formed with a reduced thickness along its side edges 904 a and 904 band end edges 906 a and 906 b. This reduced thickness may be formed by astamping operation, by grinding, machining or other mechanicaltechnique, by chemical etching or by other known techniques. As aresult, the thickness of the side and end edges of plate 902 may be lessthan the thickness of a center region 908. Once the edges of plate 902have been thinned, the plate may be deformed into an electrode 900having a curved shape that substantially matches the curvature of sheath102. Following the attachment of conductors 314, an electrode 900 may beassembled in each of cavities 154 and 156 and the distal end section 102d of sheath 102 may be subjected to a reflow heating process. Duringsuch process, the softened or molten polymer will flow to cover thethinned edges of electrodes 900 to firmly hold same in place.

FIG. 13 shows an electrode 1000 that is generally in the form of arectangular plate 1002 having a curvature that is substantially similarto the curvature of the outer surface of sheath 102. The end portions1004 and 1006 of plate 1002 are bent toward one another against theinner surface of plate 1002 as in a conventional staple so that a slightgap 1008 is formed between end portions 1004 and 1006 and the main body1010 of the plate. Following the attachment of conductors 314,electrodes 1000 may be assembled in appropriate positions near thedistal tip 120 of sheath 102 and the distal end section 102 d of thesheath may be subjected to a reflow heating process. As the polymer ofsheath 102 softens, electrodes 1000 may sink into the polymer, and thepolymer may flow into the gaps 1008 between end portions 1004 and 1006and main body 1010, securely affixing the electrode to the sheath. Thus,preforming cavities 154 and 156 in sheath 102 may not be necessary inthis embodiment. While FIG. 13 shows end portions 1004 and 1006 bent atright angles to the sides of plate 1002, that need not be the case. Endportions 1004 and 1006 may be bent at an angle other than right anglesif it is desired to produce a non-rectangular electrode surface.

FIG. 14 shows an electrode 1100 which is a variant of electrode 1000shown in FIG. 13. The difference between the electrodes is that, inaddition to main body 1108 and end portions 1104 and 1106, the plate1102 of electrode 1100 includes projections 1110 and 1112 that protrudefrom the lateral sides of the main body. In addition to folding the endportions 1104 and 1106 of plate 1102 against the inner surface of theplate, projections 1110 and 1112 may be folded inwardly until they coverthe side edges of the end portions. Relative to electrode 1000,electrode 1100 eliminates exposed sharp edges that could damage tissueand provides a more secure affixation of the electrode to sheath 102,particularly in the circumferential direction.

Different configurations for securing the electrode 1000 of FIG. 13 tosheath 102 are shown in the longitudinal cross-sectional views shown inFIGS. 15A-D. In each configuration, following the attachment of aconductor 314 to each electrode 1000, one electrode is placed into eachof cavities 154 and 156 and the distal end section 102 d of sheath 102is subjected to a reflow heating process, locking the electrodes inplace. Referring to FIG. 15A, rather than bending the end portions 1004and 1006 of plate 1002 toward one another, end portion 1006 is benttoward the inner surface of plate 1002, while end portion 1004 is bentaway from end portion 1006 and main body 1010 so that end portions 1004and 1006 lie in substantially the same plane.

FIG. 15B shows electrode 1000 attached to sheath 102 at a positionspaced from the distal tip 120 of the sheath. Both end portions 1004 and1006 are bent toward one another against the inner surface of plate 1002as described above. FIG. 15C is substantially the same as FIG. 15B.However, rather than being positioned at a spaced distance from thedistal tip 120 of sheath 102, electrode 1000 in FIG. 15C is positionedat the distal tip of the sheath so that the end of the electrode isexposed on the distal end face of the sheath. As discussed above,assembling electrode 1000 to sheath 102 in this position produces thestrongest signal from the bundle of His during a mapping procedure.

The configuration shown in FIG. 15D is similar to the configurationshown in FIG. 15A. However, rather than having one end portion benttoward the main body 1010 of plate 1002, both of end portions 1004 and1006 are bent away from one another and away from main body 1010.Bending one or more of the end portions away from main body 1010, asshown in FIGS. 15A and 15D, facilitates the secure connection ofelectrode 1000 to sheath 102 as it does not require polymer to flow intothe gaps 1008 between the end portions and the main portion 1010 of theelectrode.

Electrode 1000 may also be affixed to sheath 102 in a variant of whathas been described above in connection with FIGS. 13, 14, and 15A-15C.In each of those embodiments, at least one of end portions 1004 and 1006is bent toward the inner surface of plate 1002, creating a gap 1008between the end portion and the main body 1010 of the plate. In thevariant contemplated, a separate strip of Pebax® or other polymer may bepositioned against the inner surface of plate 1002 before the endportions are bent. Thus, after the bending operation, the strip ofPebax® or other polymer will be positioned in and fill gaps 1008.Electrode 1000 may then be assembled to sheath 102 as described above.However, during the reflow process, the sheath polymer will not have tofill gaps 1008, as those gaps will already have been filled. Rather, thepolymer in gaps 1008 will melt and fuse to the other polymer of sheath102, firmly holding electrode 1000 in place.

Another technique for attaching electrode 1000 to sheath 102 is shown inFIG. 16. In this technique, distal section 124 of outer layer 114 is notassembled to sheath 102 during the sheath assembly process. Rather,slits 160 are formed at appropriate locations in section 124. The endportions 1004 and 1006 of electrode 1000 are then bent to an orientationorthogonal to the outer layer in main body 1010 of the electrode.Electrode 1000 may then be assembled to the distal section 124 of outerlayer 114 by inserting end portions 1004 and 1006 into slits 160 andbending them against the inner surface of the sheath section. Endportions 1004 and 1006 may be bent toward one another, away from oneanother, or one end portion may be bent toward the main body 1010, whilethe other end portion is bent away from the first end portion. Withelectrode 1000 assembled to section 124 as described, this section ofouter layer 114 may be assembled over the distal end section 102 d ofsheath 102, which may again be subjected to a reflow heating process tomelt and bond the distal section 124 of outer layer 114 to theunderlying braided layer 112, trapping electrode 1000 in place.

In another variant for attaching any of the electrodes described aboveto sheath 102, the electrode may first be sandwiched between two stripsof Pebax® or other polymer. The strip of polymer on the inner surface ofthe electrode may include an aperture for connecting a conductor 314 tothe electrode. The sandwiched electrode assembly may then be properlypositioned on sheath 102 and subjected to a reflow process through whichthe electrode is strongly affixed to the sheath. Following the reflowprocess, the outer layer of polymer covering the electrode may beremoved by any known technique, including laser ablation, cutting,scraping, grinding and the like to expose the outer surface of theelectrode.

When delivery device 100 is being used to map the location of the bundleof His 30, the free ends of conductors 314 may be connected throughconnector 340 to a patient monitor, electrocardiograph, or otherexternal device for displaying the electrical signals detected byelectrodes 310 and 312. Optionally, sheath 102 may include a ringelectrode 350 (FIG. 5B) spaced proximally of mapping electrodes 310 and312. As ring electrode 350 comprises a continuous ring, it may beincorporated in sheath 102 during assembly of the sheath, usingtechniques known in the art. In order to not interfere with thesplitting or peeling of sheath 102 along its entire length, ringelectrode 350 may be skived so as to readily separate into two when thesheath is being split and removed from the pacing lead, as describedmore fully below. The fabrication and use of skived rings that may besplittable is described in U.S. Pat. No. 8,449,527, the disclosure ofwhich is hereby incorporated by reference herein. When ribs 111 extendradially to the outer surface of sheath 102, ring electrode 350 may beformed as two C-shaped sections positioned on opposite sides of the ribsin the same manner as electrodes 310 and 312. Electrical conductors (notshown) may extend from ring electrode 350 to connector 340 through tube140 or through another tube incorporated in sheath 102. When available,voltage differences between ring electrode 350 and either of splitelectrodes 310 or 312 may be used to map the electrical activity of theheart.

Sheath 102 is connected at its proximal end to handle 202. Alongitudinal cross-section of one embodiment of handle 202 is shown inFIG. 17. Handle 202 may include a distal housing portion 210 and aproximal housing portion 212, both of which are hollow. Housing portions210 and 212 may be joined to one another by a rigid alignment rail 214so as to maintain a space between the housing portions. Alignment rail214 may be formed from a rigid material, such as glass-filled nylons,acetal homopolymers and copolymers, polycarbonate, polysulfone, etc.,and may be connected to housing portions 210 and 212 by any knownfastening mechanism, including screws, press fit connection, ultrasonicwelding and the like. Prior to the connection of both ends of alignmentrail 214 to the housing portions, a hollow pull wire screw 220 may beassembled over the rail and a rotatable actuator 222 may be assembledover the screw. Actuator 222 has a series of internal threads 224 thatmate with external threads 226 on screw 220. At one end, actuator 222has an annular ring 230 that is captured within an annular groove 232 indistal housing portion 210. At its other end, actuator 222 has a similarannular ring 234 that is captured within an annular groove 236 inproximal housing portion 212. The engagement of ring 230 in groove 232,and the engagement of ring 234 in groove 236, positions actuator 222 inthe space between the housing portions, guides the rotation of theactuator in handle 202, and serves to help maintain the assembly ofdistal housing portion 210 to proximal housing portion 212. As actuator222 is rotated in a first direction, pull wire screw 220 will translateproximally relative to handle 202, and when the actuator is rotated inthe opposite direction, the pull wire screw will translate distallyrelative to the handle. The proximal end of pull wire 130 may be fedthrough pull wire screw 220 for connection in a known manner to theproximal end thereof. The distal end of pull wire 130 may be fed throughnarrow tube 132 of sheath 102 and welded to pull ring 134. Thus, as pullwire screw 220 translates proximally, it will translate pull wire 130proximally, placing the pull wire in tension and resulting in thedeflection of deflectable section 102 c of sheath 102, and when pullwire screw 220 translates distally, it will translate pull wire 130distally, leading to the movement of the pull wire and the deflectablesection 102 c of sheath 102 back to their initial and substantiallystraight positions.

Handle 202 may also include a conduit 240 having a connector 242 at itsproximal end for connection to a source of flushing fluid (FIG. 4).Conduit 240 may be connected to a further conduit 244 (FIG. 17) thattravels through handle 202 to hub 402 for supplying the flushing fluidto flush the interior of sheath 102. Conduit 320, carrying conductors314, may be connected at one end to conduit 240 by a Y-splitter, and atthe other end may be connected to electrical connector 340. Conductors314, traveling from electrodes 310 and 312 through narrow tubes 140 ofsheath 102, and through handle 202, exit therefrom through conduits 240and 320, and are then connected by soldering or the like to pins inelectrical connector 340.

Referring to FIG. 17, hub 402 protrudes from the interior of distalhousing portion 210 and fixedly connects the proximal end of sheath 102to handle 202. In one arrangement, hub 402 may be injection moldedaround the proximal end of sheath 102. Hub 402 may be formed withthinned wall regions 404 that extend along the length of the hub indiametrically opposed portions of the hub, as shown in FIG. 18A. Hub 402may be formed on or assembled to sheath 102 so that thinned regions 404are aligned with ribs 111, enabling the hub and the sheath to be splitalong a continuous substantially straight line, shown as dashed line 410in FIG. 17. Methods for forming a splittable hub are described in U.S.Pat. No. 7,377,909, the disclosure of which is hereby incorporated byreference herein. Sheath 102 may pass through a hemostasis valve (notshown) in or proximal of hub 402, which provides a seal to minimizeblood loss from around the sheath. A web 250 of a polymer or othermaterial may be formed around the exposed portion of hub 402 to firmlyaffix the hub to distal housing portion 210, and to provide a region onopposite sides of the hub that a user may grasp and pull to split thehub and sheath 102 longitudinally. Other configurations of deliverydevice 100 in which handle 202, hub 402 and connector 340 are indifferent positions relative to one another are contemplated herein andwill be described further below.

When pull wire 130 is translated proximally, the pliability of sections116 and 118 of outer layer 114 enables the deflectable section 102 c ofsheath 102 to deflect from a substantially straight configuration to thepredefined dual hinged configuration shown in FIG. 19. By deflecting atthese two spaced locations, sheath 102 assumes a shape that betterenables its distal tip 120 to be positioned to confront the right atrialwall near His bundle 30 while the proximal section 102 a of sheath 102is positioned within the superior vena cava 12 of heart 10. Distance Xin FIG. 19 is the average distance from the central axis of superiorvena cava 12, through which sheath 102 enters the right atrium RA, totricuspid valve 16, while distance Y is the average inner diameter ofthe tricuspid valve. One-third of distance Y approximates the distancewhich sheath 102 must traverse to reach the atrial wall in order tocontact or come in close proximity to His bundle 30. As this distance isan approximation, and as exceeding this distance is not likely to have anegative effect on locating His bundle 30, it will be appreciated thatthis distance (which is approximately the distance from the section 122of sheath 102 (or outer layer 114) to the distal tip 120 thereof) may bebetween about ⅓ Y and about ½ Y. Distances X and Y are illustratedrelative to the structures of heart 10 in the diagrammatic illustrationshown in FIG. 20. To complete the description, rotating actuator 222 inthe opposite direction will translate pull wire 130 distally, returningsheath 102 toward the substantially straight configuration.

Delivery device 100 may be used to deliver a pacing lead into the rightatrium RA, to map the right atrium to locate His bundle 30, and to fixthe pacing lead therein. One example of such a pacing lead is pacinglead 600 shown schematically in FIG. 21. Lead 600 generally has aflexible elongate body 602 with a proximal end 604, a distal end 606,and a lumen (not shown) extending axially therethrough. A pair ofbipolar electrodes 608, 610 is located at the distal end of body 602.Electrode 610 is positioned at the distal tip of body 602, whileelectrode 608 may be spaced therefrom along the length of the body. Afixation anchor 612 extends distally from the distal end 606 of body 602and forms a part of electrode 610. At the proximal end 604 of body 602,lead 600 includes a pair of electrical contacts 614 and 616. Contacts614 and 616 are each electrically connected to one of electrodes 608 and610 by conductors traveling through the lumen in body 602. Contacts 614and 616 enable pacing lead 600 to be mechanically and electricallyconnected to pacemaker 52, such as by alligator clips or otherconnectors connected to contacts 614 and 616.

The use of delivery device 100 to deliver and fix pacing lead 600 in thebundle of His 30 will now be described with reference to FIGS. 22A-D and23. FIGS. 22A-D illustrate the delivery and fixation of pacing lead 600with respect to an anatomically-accurate transparent model 700 of theright side of the human heart. Model 700 may be used to train operatorsin the His pacing procedure, and to develop and test clinical tools forperforming the procedure. For clarity, the reference numerals used inFIGS. 22A-D to identify the structures of the heart will be the samereference numbers used to identify the structures in the cutaway view ofthe heart illustrated in FIG. 1. The region in which the bundle of Hisis located is simulated in model 700 by a conductive insert (not shown)that may be received in port 710. The insert may be formed of a gel toenable fixation of pacing lead 600 therein and may have physical and/orelectrical properties that simulate myocardial tissue. The insert mayalso be doped with an ionic material to provide electrical propertiessimilar to those of the His bundle so that electrically-active deliverydevices can be used to map the region. During a mapping and fixationprocedure, the insert may be stimulated electrically by a circuit toproduce an electric signal, preferably one that is similar to thatproduced by the bundle of His. A more detailed description of model 700and its use can be found in commonly owned patent application Ser. No.16/208,348, the disclosure of which is hereby incorporated by referenceherein.

With conductors 314 electrically connected through connector 340 to anexternal device for receiving signals from electrodes 310 and 312,delivery device 100 is inserted through a vascular access site into thesuperior vena cava 12 and is maneuvered through the superior vena cavato the right atrium RA as illustrated in FIGS. 22A and 22B. During thisinsertion procedure, the sheath 102 of delivery device 100 may have asubstantially straight configuration and may include a dilator (notshown) positioned in the lumen 126 thereof to enlarge the access pathand to provide support to the sheath as it is being maneuvered. Thestraight configuration of sheath 102 facilitates its passage through thesuperior vena cava 12 and into the right atrium RA. Once the distal tip120 of delivery device 100 has entered the right atrium RA, the dilatormay be removed from the delivery device and pacing lead 600 may beinserted into lumen 126 in its place. Again, the straight configurationof sheath 102 facilitates the insertion of pacing lead 600 therein.

With the distal portion of sheath 102 fully within right atrium RA, theuser may operate delivery device 100 to place sheath 102 in thedeflected configuration shown in FIG. 22C. Since sheath 102 is only ableto deflect in a single direction, the user must first confirm thatdelivery device 100 is in the proper orientation. This may beaccomplished by locating the position of indicia (not shown) in theproximal section 102 a of sheath 102 or on handle 202, by thenonsymmetrical shape of the handle or by another indicator. Suchindicator preferably will identify the side of sheath 102 on which pullwire 130 is located, which is the direction to which the deflectablesection 102 c of the sheath will deflect. Once the proper orientation ofsheath 102 has been confirmed, the user may operate the actuator 222 onthe handle 202 of delivery device 100 to move the deflectable section102 c of the sheath to the deflected configuration. With the proximalsection 102 a of sheath 102 positioned in the superior vena cava 12 andthe deflectable section 102 c of the sheath deflected as shown in FIG.22C, the distal tip 120 of the sheath will point generally toward theregion in the atrial septum at which the bundle of His 30 is located,and will be in close proximity to the septum, as shown in FIG. 22D. Ifelectrical signals are received from electrodes 310 and 312 in thisposition of sheath 102, the user will know that the distal tip 120 ofthe sheath is aligned with His bundle 30.

If electrodes 310 and 312 are not receiving electrical signals, or ifthe signals are very faint, the user may maneuver the distal tip 120 ofsheath 102 by small movements of actuator 222 in either a forward orreverse direction to scan the atrial wall. These small movements ofactuator 222 will deflect the deflectable section 102 c of sheath 102 bysmall amounts toward or away from the proximal section 102 a of thesheath. Scanning in different directions can be accomplished by smallrotations of handle 202, which rotates the distal end section 102 d ofsheath 102 about the longitudinal axis of the sheath. When the signalsreceived by electrodes 310 and 312 are the strongest, the user can beconfident that His bundle 30 has been located, and the close proximityof the electrodes to one another will assure that the His bundle isdirectly opposite the distal tip 120 of sheath 102. With each of thesemovements, the distal tip 120 of sheath 102 remains generallyperpendicular to the atrial wall. Accordingly, once this mappingprocedure has located the bundle of His, pacing lead 600 can be fixed inthe His bundle by advancing the fixation anchor 612 of the lead out fromthe distal tip 120 of sheath 102 and rotating the lead within deliverydevice 100 to drive the fixation anchor into the atrial septal wall, asshown schematically in FIG. 22. Since the overall stiffness of sheath102 is relatively high, the distal tip of the sheath will maintain itsposition as fixation anchor 612 is driven into the atrial septal wall,thereby assuring that the fixation anchor will not be diverted from itstarget site.

Once lead 600 has been properly fixed in the tissue of the bundle ofHis, sheath 102 may be returned to a substantially straightconfiguration by rotating actuator 222 in the direction opposite thatused for deflection. Sheath 102 may then be removed from around lead 600and from heart 10. This may be accomplished by pulling the oppositesides of hub 402 away from one another to separate the hub along thinnedregions 404. Continued pulling of the sides of hub 402 away from oneanother will cause the sides of sheath 102 on opposite sides of ribs 111to move away from one another to split the sheath in half along itslength. After hub 402 and an initial length of sheath 102 has been splitin half, the user may apply forward pressure to pacing lead 600 whilepulling the sheath proximally to expose a next length of the sheath.This next length of sheath 102 may then be split in two by pulling thesides of the sheath in opposite directions. The user may then againapply forward pressure to pacing lead 600 while withdrawing a furtherlength of sheath 102 proximally. This process may be continued untilsheath 102 has been split into two along its entire length and removedfrom lead 600, leaving the lead embedded within the atrial septal wallat the bundle of His.

Although the sheath 102 of delivery device 100 has been described asincluding a liner 110 having square or rectangular ribs 111 that arecovered by outer layer 114, it is contemplated that liner 110 may haveone or more ribs with a variety of different shapes and/or sizes, andthese ribs may extend to the outer surface of the sheath, may be coveredby outer layer 114, or may have other configurations. Cross-sections ofsheath 102 having at least some of these different configurations areshown in FIGS. 7A-7K.

FIG. 7A shows the cross-section of a sheath 102.1 that is substantiallythe same as that of sheath 102 shown in FIG. 5C. However, rather thanhaving outer layer 114 formed as a complete tube with recesses 115 formating with ribs 111, the outer layer of sheath 102.1 is thinner thanthat of sheath 102 and is formed as two C-shaped sections 114 a and 114b that are assembled to the sheath on opposite sides of ribs 111. As aresult, ribs 111 may extend to the outer surface of sheath 102.1. Whilethis configuration may require additional assembly steps not requiredfor the configuration of sheath 102 shown in FIGS. 5A-C, the fact thatribs 111 are exposed on the outer surface of sheath 102.1 providesimproved peelability over that of sheath 102.

The configuration of sheath 102.2 shown in FIG. 7B is similar to that ofsheath 102.1 shown in FIG. 7A. However, the C-shaped outer sections 114a and 114 b of sheath 102.2 have a thickness that is similar to thethickness of outer layer 114 in sheath 102. Rather than extrude a verythin section of outer layer 114 overlying ribs 111, separate strips ofmaterial 119 overlapping the ribs may be coextruded with the outerlayer. Strips of material 119 may be formed of similar polymer materialsto those used to form outer layer 114, but they generally have somedesirable material properties, e.g. improved peelability and/or surfacelubricity.

As noted above, it is desirable to have sheath 102 bend smoothly whendeflected during use. However, it is known that the PTFE liner 110 withribs may have a tendency to kink when bent because of its limitedmechanical strength. This may also cause the deflection of the sheath tonot occur in a plane. The configuration of sheath 102.3 shown in FIG. 7Caddresses these issues by providing a reinforcing ribbon 121 on eachside of ribs 111 along the length of the sheath, or at least along thelength of deflectable section 102 c. Ribbons 121 may be formed fromstainless steel or high-performance engineering polymers including, butnot limited to, polyetherimide, aromatic polyamides, polysulfones,polyether sulfones, aromatic polyesters and liquid crystal polymers.Aside from ribbons 121, sheath 102.3 has substantially the sameconfiguration as sheath 102 of FIG. 5C.

The configuration of sheath 102.4 shown in FIG. 7D is substantially thesame as the configuration of sheath 102.1 described above. However,sheath 102.4 incorporates reinforcing ribbons 121 on either side of ribs111 along the length of the sheath, or at least along the length ofdeflectable section 102 c. Similarly, the configuration of sheath 102.5shown in FIG. 7E is substantially the same as the configuration ofsheath 102.2 shown in FIG. 7B but includes reinforcing ribbons 121 onthe sides of ribs 111 along the length of the sheath or at least alongthe length of deflectable section 102 c.

It is also contemplated that the ribs 111 in sheath 102 may have a shapethat is other than square or rectangular. Thus, FIG. 7F shows a sheathin which ribs 111 are trapezoidal, FIG. 7G shows a sheath in which ribs111 are triangular, and FIG. 7H shows a sheath in which ribs 111 aresemi-circular. In each of these configurations, the outer layer of thesheath is formed as two C-shaped sections 114 a and 114 b that areassembled to the sheath on opposite sides of ribs 111, the ends of theC-shaped sections being shaped to correspond to and mate with the shapeof the ribs. The ribs 111 in these embodiments extend to the outersurface of the sheath. FIGS. 71, 7J and 7K illustrate sheaths havingtrapezoidal, triangular and semi-circular ribs 111, respectively, butinclude an outer layer 114 that is formed as a continuous tube havingone or more inner recesses 115 that correspond to the shape and size ofthe ribs.

As noted, it is contemplated that delivery device 100 may be configureddifferently, with handle 202, hub 402 and electrical connector 340arranged in different relative positions than described above. Variousconfigurations of delivery device 100 are shown schematically in FIGS.24A-C. FIG. 24A is a highly schematic view of an embodiment of deliverydevice 100 that is very similar to that shown in FIG. 4. In the deliverydevice of this embodiment, sheath 102 enters a splittable tubularstructure 204 at the distal end of handle 202 in an orientation that iscoaxial with the handle. Tubular structure 204 may be formed in a mannersimilar to hub 402, e.g., with thinned walls in the regions along whichthe tubular structure is to split. As shown in FIG. 24A, tubularstructure 204 may not split apart along its entire length but may splitapart only partially along its length. Sheath 102 then curves toward asplittable hub 402 at the top of handle 202. Hub 402 is secured tohandle 202 by web 250, which provides a region on opposite sides of thehub for a user to grasp and pull apart to split the hub, tubularstructure 204 and sheath 102 longitudinally along a split line or splitplane, shown as the heavy line 252. Electrical connector 340 ispositioned at the proximal end of handle 202. Connector 340 may beoriented at an oblique angle to handle 202, as shown in FIG. 4, or maybe colinear with the handle, as shown in FIG. 24A.

An alternate embodiment of delivery device 100 is shown in FIG. 24B. Inthis embodiment, handle 202 extends at an oblique angle from the top ofsplittable tubular structure 204, while electrical connector 340 extendsat a similar oblique angle from the bottom of the tubular structure. Afirst web 250 a secures handle 202 to tubular structure 204, and asecond web 250 b secures electrical connector 340 to the tubularstructure. Splittable hub 402 is positioned at the proximal end oftubular structure 204. To remove sheath 102 from pacing lead 600 in thisembodiment, the user may grasp opposite sides of hub 402, pulling themaway from one another to split the hub, tubular structure 204 and thensheath 102 longitudinally along split line or split plane 252. Thisembodiment enables forward pressure to be applied to pacing lead 600 ina linear direction and sheath 102 to be retracted in a linear directionas the splitting of the sheath advances along its length.

The embodiment of FIG. 24C is similar to the embodiment of FIG. 24A.However, rather than having electrical connector 340 positioned at theproximal end of handle 202 coaxially with the handle, the connector inFIG. 24C projects at an oblique angle from the bottom of splittabletubular structure 204. A first web 250 a secures splittable hub 402 totubular structure 204, while a second web 250 b secures electricalconnector 340 to the tubular structure. To remove sheath 102 from pacinglead 600 in this embodiment, the user may grasp and pull apart oppositesides of hub 402, tubular structure 204 and sheath 102 along split line252.

To summarize the foregoing, according to a first aspect of thedisclosure, a delivery device for delivering a pacing lead to the Hisbundle of a patient's heart includes a handle; an elongated sheathhaving a proximal end connected to the handle and a distal end remotefrom the handle, a distal portion of the sheath having a plurality offlexible sections spaced from one another along a length of the sheath,the sheath having a longitudinal rib extending from the proximal end tothe distal end and being splittable along a first split line from theproximal end to the distal end; a pull wire having a distal endconnected to the sheath distally of the flexible sections and extendingto a proximal end; and a plurality of mapping electrodes positioned atthe distal end of the sheath; and or

the distal end of the sheath may have a distal tip, and the mappingelectrodes may include two electrodes positioned on opposite sides ofthe rib at positions spaced from the distal tip of the sheath; and/or

the two electrodes may be spaced apart by between about 1 mm and about 3mm in a circumferential direction of the sheath; and/or

the distal end of the sheath may have a distal end face, and the mappingelectrodes may be exposed on the distal end face; and/or

the distal end of the sheath may have a distal end face, and the mappingelectrodes may be spaced from the distal end face; and/or

the flexible portions of the sheath may have a first Shore D hardnesswhich is less than a second Shore D hardness of remaining portions ofthe sheath; and/or

the flexible portions of the sheath may have a Shore D hardness ofbetween about 20 and about 40; and/or

the flexible portions of the sheath may have a Shore D hardness of about35; and/or

the remaining portions of the sheath may have a Shore D hardness ofbetween 60 and about 100; and/or

the remaining portions of the sheath may have a Shore D hardness ofbetween 70 and about 75; and/or

the delivery device may further include a hub at the proximal end of thesheath, the hub having a weakened region defining a second split linelongitudinally aligned with the first split line in the sheath; and/or

the handle may include a rotatable portion and a translatable portion,the proximal end of the pull wire being connected to the translatableportion, whereby rotation of the rotatable portion translates the pullwire in a longitudinal direction of the sheath; and/or

the handle may include a proximal handle portion and a distal handleportion, the proximal handle portion being connected to the distalhandle portion by a rail so as to define a space between the proximalhandle portion and the distal handle portion; and/or

the handle may include a rotatable actuator positioned in the space andconnected to the proximal handle portion and the distal handle portion,rotation of the actuator in a first direction bending the flexiblesections of the sheath toward a dual hinged configuration and rotationof the actuator in an opposite direction moving the sheath toward asubstantially straight configuration; and/or

the handle may have a longitudinal axis and the proximal end of thesheath may enter the handle along the longitudinal axis and may exit thehandle at an angle transverse to the longitudinal axis; and/or

the handle may have a longitudinal axis and the proximal end of thesheath may enter the handle at a predetermined angle transverse to thelongitudinal axis and may exit the handle at the predetermined angletransverse to the longitudinal axis; and/or

each of the mapping electrodes may include a pair of side edgessubstantially parallel to a longitudinal axis of the sheath and a pairof end edges substantially orthogonal to the longitudinal axis of thesheath, and the side edges may be beveled; and/or

each of the electrodes may be formed from a plate having a pair ofopposed side edges and a pair of opposed end edges, and the plate mayhave a thickness along the side edges and along the end edges that isless than the thickness in a center of the plate; and/or

each of the electrodes may have a main body and a pair of end portionsprojecting from opposite ends of the main body; and/or

the end portions may project away from the main body in oppositedirections; and/or

the main body may have an inner surface and an outer surface, and atleast one of the end portions may be bent against the inner surface ofthe main body; and/or

the pair of end portions may be bent toward one another and toward theinner surface of the main body; and/or

the sheath may include an inner layer or liner, a middle or braidedlayer, and an outer layer, the longitudinal rib being formed on theinner layer and extending through the middle layer; and/or

the longitudinal rib may extend through the outer layer; and/or

the inner layer may extend from the proximal end of the sheath to thedistal end of the sheath; and/or

the inner layer may be formed from a lubricious material; and/or

the lubricious material may be polytetrafluoroethylene; and/or

the inner layer may include platelet-like fibrils oriented in alongitudinal direction of the sheath; and/or

the middle layer may be a braided layer including metallic braidsembedded within a polymer; and/or

the braided layer may extend from the proximal end of the sheath to thedistal end of the sheath; and/or

the outer layer may include a plurality of sections formed from apolymer having a first shore D hardness and a plurality of sectionsformed from a polymer having a second shore D hardness which is greaterthan the first shore D hardness; and/or

the dual hinged configuration of the sheath may define a deflectionplane, and the mapping electrodes may include two electrodes that arepositioned on the sheath so that the two electrodes lie within thedeflection plane in the dual hinged configuration; and/or

the sheath may have a second longitudinal rib extending from theproximal end to the distal end, the second longitudinal rib beingdiametrically opposed to the first longitudinal rib, the sheath beingsplittable along another split line from the proximal end to the distalend.

According to another aspect of the disclosure, a method for delivering apacing lead to the His bundle of a patient's heart includes providing adelivery device having a sheath with a proximal end, a distal end, a ribextending from the proximal end to the distal end, an axial lumen and adistal end face; inserting the sheath into the patient's body throughthe superior vena cava until a distal end section of the sheath ispositioned in the right atrium of the patient; inserting a pacing leadinto the axial lumen of the sheath; deflecting the distal end section ofthe sheath so that the distal end face of the sheath confronts the wallof the right atrium; moving the distal end face of the sheath relativeto the wall of the right atrium until electrodes adjacent the distal endface of the sheath receive electrical signals from the His bundle;fixing the pacing lead to tissue at the His bundle; and splitting thesheath along a first split line from the proximal end to the distal endto remove the sheath from the pacing lead; and/or

the delivery device may include a handle connected to a proximal end ofthe sheath and a pull wire extending from the handle to a distal endsection of the sheath, and the deflecting step may include translatingthe pull wire proximally relative to the handle; and/or

the handle may include a rotatable actuator, and the deflecting step mayinclude rotating the actuator in a first direction to move the pull wireproximally relative to the handle; and/or

the distal end portion of the sheath may include a plurality of flexiblesections spaced from one another along a length of the sheath, and thedeflecting step may include bending the sheath at the flexible sectionsto place the distal end section of the sheath in a dual hinged curvedconfiguration; and/or

the method may further include the step of fixing the pacing lead totissue in the bundle of His.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims. For example,although the delivery device has been described herein for use inmapping the bundle of His and fixing a pacing lead therein, the deliverydevice may also be used as a component of an ablation catheter to ablatethe bundle of His. In such event, the heart could be paced usingmultiple leads in various chambers of the heart.

What is claimed is:
 1. A delivery device for delivering a lead to apatient's heart, the delivery device comprising: a handle; and anelongated sheath comprising: a proximal end connected to the handle anda distal end remote from the handle; a distal portion of the sheathhaving a plurality of flexible sections spaced from one another along alength of the sheath; a first layer having a longitudinal rib thatprotrudes radially outward from an outer surface of the first layer, thelongitudinal rib extending along the length of the sheath; a first splitline extending along the sheath; and a second layer surrounding thefirst layer, the second layer having a recess facing radially inward andmating with the rib, the first split line aligned with the rib and therecess to facilitate splitting of the sheath.
 2. The delivery device ofclaim 1, further comprising a plurality of mapping electrodes positionedat the distal end of the sheath, wherein the plurality of mappingelectrodes comprise two electrodes that are spaced between 1 mm and 3 mmin a circumferential direction of the sheath.
 3. The delivery device ofclaim 2, wherein the distal end of the sheath has a distal end face, andthe mapping electrodes are exposed on the distal end face.
 4. Thedelivery device of claim 1, wherein the longitudinal rib extends fromthe proximal end to the distal end, the sheath being splittable alongthe first split line from the proximal end to the distal end;
 5. Thedelivery device of claim 1, wherein the flexible sections of the sheathhave a Shore D hardness of between 20 and
 40. 6. The delivery device ofclaim 5, wherein the flexible sections of the sheath have a Shore Dhardness of
 35. 7. The delivery device of claim 5, wherein remainingsections of the sheath have a Shore D hardness of between 60 and
 100. 8.The delivery device of claim 7, wherein the remaining sections of thesheath have a Shore D hardness of between 70 and
 75. 9. The deliverydevice of claim 1, further comprising a hub at the proximal end of thesheath, the hub having a weakened region defining a second split linelongitudinally aligned with the first split line in the sheath.
 10. Thedelivery device of claim 1, wherein the delivery device is configured toposition the distal end of the sheath proximate at least one of a HISbundle, a position along the septum wall proximate to a left bundlebranch, or a position along the septum wall proximate to a right bundlebranch.
 11. The delivery device of claim 1, wherein the distal portionof the sheath is configured to pass through a vascular access site intothe right atrium (RA) and the pull wire is configured to deflect thedistal portion of the sheath to locate the plurality of mappingelectrodes proximate to the His bundle.
 12. The delivery device of claim1, wherein the handle includes a proximal handle portion and a distalhandle portion, the proximal handle portion being connected to thedistal handle portion by a rail to define a space between the proximalhandle portion and the distal handle portion.
 13. The delivery device ofclaim 12, further comprising a rotatable actuator positioned in thespace and connected to the proximal handle portion and the distal handleportion, rotation of the actuator in a first direction bending theflexible sections of the sheath toward a dual hinged configuration androtation of the actuator in an opposite direction moving the sheathtoward a substantially straight configuration.
 14. The delivery deviceof claim 1, wherein the sheath has a second longitudinal rib extendingalong the length of the sheath, the second longitudinal rib beingdiametrically opposed to the first longitudinal rib, the sheath beingsplittable along a second split line, the second split line aligned withthe second longitudinal rib.
 15. The delivery device of claim 1, whereinthe second longitudinal rib extends from the proximal end to the distalend, and the sheath is splittable along the second split line from theproximal end to the distal end.
 16. The delivery device of claim 1,wherein the first layer is formed from polytetrafluorethylene.
 17. Thedelivery device of claim 1, wherein the first and second layersrepresent inner and outer layers, the sheath further including a middlelayer, the longitudinal rib extending through the middle layer.
 18. Thedelivery device of claim 1, wherein the sheath includes at least two ofthe inner layer, a middle layer and the outer layer, the rib extendingalong one of the inner layer or middle layer, the recess provided inanother of the middle layer or outer layer, the rib and recess matingwith one another.
 19. The delivery device of claim 1, further comprisinga pull wire having a distal end connected to the sheath distally of theflexible sections and extending to a proximal end.
 20. The deliverydevice of claim 1, wherein the pull wire is configured to deflect thedistal portion of the sheath to locate the plurality of mappingelectrodes proximate to the His bundle.